1. Field
The present disclosure relates generally to position estimation techniques and, more particularly, to position estimation for use in or with mobile communication devices.
2. Information
Mobile communication devices, such as, for example, cellular telephones, portable navigation units, laptop computers, personal digital assistants, or the like are becoming more common every day. Certain mobile communication devices, such as, for example, location-aware cellular telephones, smart telephones, or the like may assist users in estimating their geographic locations by providing position information obtained or gathered from various systems. For example, in an outdoor environment, certain mobile communication devices may obtain a position estimate or so-called “position fix” by acquiring wireless signals from a satellite positioning system (SPS), such as the global positioning system (GPS) or other like Global Navigation Satellite Systems (GNSS), cellular base station, location beacon, or the like via a cellular telephone or other wireless communications network. In some instances, received wireless signals may be processed by or at a mobile communication device, and its location may be estimated using known techniques, such as, for example, Advanced Forward Link Trilateration (AFLT), base station identification, or the like.
In an indoor environment, some mobile communication devices may be unable to reliably receive or acquire satellite or like wireless signals to facilitate or support one or more position estimation techniques. For example, signals from an SPS or other wireless transmitters may be attenuated or otherwise affected in some manner (e.g., insufficient, weak, fragmentary, etc.), which may at least partially preclude their use for position estimations. As such, in an indoor environment, different techniques may be employed to enable navigation or location services. For example, a mobile communication device may obtain a position fix by measuring ranges to three or more terrestrial wireless access points positioned at known locations. Ranges may be measured, for example, by obtaining a Media Access Control identifier (MAC ID) address from wireless signals received from suitable access points and measuring one or more characteristics of received signals, such as signal strength, round trip delay, or the like.